methodical.impl.combo.operator — robhanlon22/methodical 0.10.1-alpha

Method combinations strategies based on the non-default method combination types in CLOS. All non-default method combinations follow the same basic pattern:

(operator (primary-method-1 args) (primary-method-2 args) (primary-method-3 args)))

(Example from "Object-Oriented Programming in Common Lisp", Keene 1988.)

The non-default method combinations each support primary methods and :around methods, but not :before or :after. Unlike the standard combination, primary methods do not support call-next-method (next-method in Methodical).

There are 9 built-in method combinations types in CLOS, excluding standard: progn, append, list, nconc, and, or, max, min, and +. These are mostly the same in the implementation below, with the following exceptions:

• The progn combo is instead named do, which you probably could have guessed.

• list has been replaced by seq, which returns a lazy sequence -- a very Clojurey improvement.

• Both nconc and append concatenate lists, but nconc does it destructively; append copies all arguments except the last. The Clojure equivalent of either is concat which is what I have named the method combination below. We actually do one better than CLOS and return a lazy sequence, but lazy-cat seemed like a cumbersome name for the combo.

One last difference: unlike CLOS operator method combinations, primary method implementations are not qualfied by their operator.

;; CLOS (defmethod total-electric-supply + ((city city)) ...)

;; Methodical (defmethod total-electric-supply :city [city] ...)

defoperator clj macro

(defoperator operator-name [methods-binding invoke-binding] & body)

Define a new operator that can be used as part of an OperatorMethodCombination. See examples below for more details.

operator clj multimethod

(operator operator-name)

Define a new operator that can be used as part of an OperatorMethodCombination. See examples below for more details. Prefer using the defoperator macro to adding a method to this directly.

operator-method-combination clj

(operator-method-combination operator-name)

Create a new method combination using the operator named by operator-name, a keyword name of one of the defoperator forms above or defined externallly.

(operator-method-combination :max)